The PITSLRE protein kinases are CDKs that include more than 20 different isoforms and are ubiquitously expressed. Little is known about their function. The PITSLRE p110 kinase isoforms are localized to the nucleoplasm and nuclear speckles, regions composed of intrachromatin granule clusters (IGCs), which are storage and assembly sites for transcription/RNA processing factors. The applicant has found that PITSLRE p110 kinase interacts directly with RNPS1, a general RNA splicing factor, and EKK2, a transcriptional elongation factor, in vitro and in vivo. PITSLRE p110 also associates with RNAPII and CKII in vivo. CKII phosphorylates a very specific portion of the imperfect repeat region of the RNAPII CTD as well as a specific region of the amino terminal domain of PITSLRE p110 in vitro. The current proposal will address the hypothesis that PITSLRE p110 kinases regulate transcription, RNA processing, or both and that its association with CKII plays a role in these functions an/or the localization of this kinase within the nucleus. PITSLRE p110 complexes will be biochemically purified and characterized from the nucleoplasm and the IGC. Its substrates and regulators will be identified. The applicant will determine if CKII phosphorylates PITSLRE p110 and the CTD in vivo and also assess the biological consequences of the phosphorylation. Finally the role of the various PITSLRE kinase isoforms will be examined by knocking-out the genes in mice.